[GIT PULL] cgroup changes for v5.20-rc1

[Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>]

The following changes since commit e71e60cd74df9386c3f684c54888f2367050b831:

  Merge tag 'dma-mapping-5.19-2022-06-06' of git://git.infradead.org/users/hch/dma-mapping (2022-06-06 17:56:18 -0700)

are available in the Git repository at:

  git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup.git/ tags/cgroup-for-5.20

for you to fetch changes up to 265792d0dede9259f0ca56bb3efcc23eceee7d01:

  cgroup: Skip subtree root in cgroup_update_dfl_csses() (2022-07-28 07:26:30 -1000)

----------------------------------------------------------------
Several core optimizations:

* threadgroup_rwsem write locking is skipped when configuring controllers in
  empty subtrees. Combined with CLONE_INTO_CGROUP, this allows the common
  static usage pattern to not grab threadgroup_rwsem at all (glibc still
  doesn't seem ready for CLONE_INTO_CGROUP unfortunately).

* threadgroup_rwsem used to be put into non-percpu mode by default due to
  latency concerns in specific use cases. There's no reason for everyone
  else to pay for it. Make the behavior optional.

* psi no longer allocates memory when disabled.

along with some code cleanups.

----------------------------------------------------------------
Chen Wandun (1):
      psi: dont alloc memory for psi by default

Lin Feng (2):
      cgroup.c: add helper __cset_cgroup_from_root to cleanup duplicated codes
      cgroup.c: remove redundant check for mixable cgroup in cgroup_migrate_vet_dst

Tejun Heo (4):
      cgroup: Elide write-locking threadgroup_rwsem when updating csses on an empty subtree
      cgroup: Add "no" prefixed mount options
      cgroup: Make !percpu threadgroup_rwsem operations optional
      cgroup: remove "no" prefixed mount options

Waiman Long (1):
      cgroup: Skip subtree root in cgroup_update_dfl_csses()

 Documentation/admin-guide/cgroup-v2.rst |   8 ++
 include/linux/cgroup-defs.h             |  21 ++++-
 include/linux/cgroup.h                  |   2 +-
 init/Kconfig                            |  10 +++
 kernel/cgroup/cgroup-internal.h         |   1 +
 kernel/cgroup/cgroup-v1.c               |  17 +++-
 kernel/cgroup/cgroup.c                  | 136 ++++++++++++++++++++------------
 kernel/sched/psi.c                      |  19 +++--
 8 files changed, 151 insertions(+), 63 deletions(-)